title: Organic anion transporting polypeptides (OATPs): regulation of expression and function.
abstract: Eleven members of the human organic anion transporter (OATP) family (grouped into six families) facilitate the Na(+)- independent transmembrane transport of various endo- and xenobiotics (bile acids, bilirubin, steroid hormone conjugates, thyroid hormones, prostaglandins, clinically used drugs, and toxins). OATPs are 12-transmembrane glycoproteins (643-722 amino acids) and contain many conserved structural features, for example, eleven cysteines in the large extracellular loop 5. They are important for proper transport, for which translocation of substrates through a central, positively-charged pore in a rocker-switch-type mechanism has been proposed. Although OATPs are expressed in various cells and tissues, some members show a more restricted pattern (well-studied OATP1B1/OATP1B3 in liver, OATP4C1 in kidney, and OATP6A1 in testis). In cancer, the distribution pattern is no longer maintained, and OATPs, like OATP1B3, become upregulated in malignant tissues (colon, breast, prostate). Studies in cell lines and animal models further revealed that the expression of OATPs is regulated in a cell- and tissue-specific way by cytokines and activation of nuclear receptors (LXR, FXR, PXR, CAR, HNF4). Also epigenetic mechanisms and postranslational modifications influence their expression and function. Therefore, changes in the expression of OATPs under pathological conditions will influence transport processes causing an altered accumulation of OATP substrates in cells of excretory organs (intestine, liver, kidney) and on various blood/organ barriers (such as brain, testis, placenta). For drugs, this may result in increased toxicity and adverse drug reactions. Therefore, it is important to improve the knowledge on the regulation and function of individual OATPs, and to apply it for therapeutic considerations.
authors.affiliation: Department of Pathophysiology and Allergy Research, Center for Pathophysiology, Infectiology, and Immunology, Medical University of Vienna, Austria.
authors.forename: Martin
authors.initials: M
authors.lastname: Svoboda
authors.forename: Juliane
authors.initials: J
authors.lastname: Riha
authors.forename: Katrin
authors.initials: K
authors.lastname: Wlcek
authors.forename: Walter
authors.initials: W
authors.lastname: Jaeger
authors.forename: Theresia
authors.initials: T
authors.lastname: Thalhammer
mesh_terms: D000818:Animals; D000970:Antineoplastic Agents / Q000494:pharmacology; D002779:Cholestasis / Q000378:metabolism; D016207:Cytokines / Q000502:physiology; D019175:DNA Methylation / Q000502:physiology; D005786:Gene Expression Regulation / Q000187:drug effects / Q000502:physiology*; D012739:Gonadal Steroid Hormones / Q000502:physiology; D006801:Humans; D008099:Liver / Q000187:drug effects / Q000201:enzymology; D023421:Models, Animal; D008954:Models, Biological; D027361:Organic Anion Transporters / Q000096:biosynthesis* / Q000737:chemistry / Q000235:genetics* / Q000502:physiology*; D054731:PDZ Domains; D004364:Pharmaceutical Preparations / Q000378:metabolism; D010766:Phosphorylation; D011499:Protein Processing, Post-Translational / Q000502:physiology; D018160:Receptors, Cytoplasmic and Nuclear / Q000378:metabolism; D016415:Sequence Alignment; D014118:Toxins, Biological / Q000378:metabolism
chemical_list: D000970:Antineoplastic Agents; D016207:Cytokines; D012739:Gonadal Steroid Hormones; D027361:Organic Anion Transporters; D004364:Pharmaceutical Preparations; D018160:Receptors, Cytoplasmic and Nuclear; D014118:Toxins, Biological